1. Field of the Invention
The present invention relates to a receiving apparatus for spread spectrum communications, and more particularly, to a spread spectrum receiving apparatus with a battery saving function used in mobile communications.
2. Description of the Related Art
In a spread spectrum communications system, a data signal is multiplied by a spread reference code, i.e., a unique pseudorandom noise (PN) code to spread the data signal. Then, the spread data signal is transmitted. On the other hand, in a spread spectrum receiving apparatus, a received signal is multiplied by the same spread reference code to demodulate the received signal. Since noise added to the received signal in a propagation path is spread by the demodulation, the spread spectrum communications system is characterized by its privacy and interference tolerance, and therefore, has been developed for mobile phones, wireless local area networks (LANs), and the like.
In a prior art spread spectrum receiving apparatus, a carrier detecting circuit for detecting a carrier in a spread spectrum modulated signal is continuously operated even in a standby mode. This will be explained later in detail.
However, particularly, when the above-described prior art spread spectrum receiving apparatus is applied to mobile communications, the power dissipation of a battery for driving the apparatus is remarkably increased.